Being poor really is a headache.

New research finds a compelling link between migraines and financial instability. A study presented Saturday at the annual conference for the European College of Neuropsychopharmacology has identified certain mutations in the CLOCK gene, a gene associated with the sleep-wake cycle—also known as the circadian rhythm—that make chronic stress-triggered migraines more common.

Xenia Gonda, an assistant professor of psychiatry and psychotherapy at Semmelweis University in Budapest, Hungary, says the findings—based on more than 2,000 people—supports the idea that stress can both interrupt normal sleep and trigger headaches. 

“This is very important to look at beyond anecdotal, to be able to understand it on the genetic level and biochemical level exactly how different stress sources—possibly through different pathways—destructs functioning and leads to manifestations of different disorders like migraines,” says Gonda.

Gonda says “financial stress was used as a proxy” because it a chronic type of stress that weighs a person down persistently, unlike, say, a work deadline. However, she says “it is possible that different types of stressors have different pathways,” though this hasn’t been proven yet.

There are an estimated 39 million adults and children in the U.S. and 1 billion migraine sufferers worldwide, a condition that definitely causes sleep loss and interferes with job performance (and therefore potential earnings). A study conducted by researchers with the American Headache Society found people with 15 or more migraine incidents per month lost approximately 4.5 hours of work productivity each week.

For the study, Gonda and her co-researchers, lead researcher Gabriella Juhasz from the University of Manchester, along with first author Daniel Baksa of Semmelweis University, evaluated 999 patients from Budapest and 1,350 from Manchester. The researchers were looking specifically at two variants in the CLOCK gene to determine whether they’re associated with migraines. The researchers didn’t find a consistent link between migraines and these gene mutations alone, but when they added in the factor of financial stress—measured with self-reported questionnaires—the impact of these specific mutations stood out. They found these particular gene variants increased the odds of having migraines in subjects who suffered from financial hardship by around 20 percent.

Gonda explains the variants in CLOCK impact communication that tells the gene how much of a certain protein to release. This protein is involved in the body’s circadian rhythm functioning. The variants in the gene identified by the researchers appears to inhibit this particular function. As a result, migraines may be more common when a a person faces chronic stress, the research suggests.

Gonda says that while their study doesn’t show the cause of migraines, it does demonstrate that migraine sufferers most likely experience the condition as a result of both genetic and environmental factors. Migraine triggers are different in every person and can include everything from hormones and lack of sleep, to weather changes and food sensitivities. However, many migraine sufferers don't know the cause of their condition, which is why doctors often attribute the condition to stress. 

“It’s not possible always to avoid stress, but that is why we need to understand which pathways actually trigger these disorders,” says Gonda.